Whenever changes you made on the structure of your database do not take effect when you reopen your database such that it appears that the modification you made did not get saved, check to make sure your structure file is not set to read-only. Also, whenever you run into an alert message stating that your data file is locked and cannot be opened, as in the example below, make sure you provide read/write access (not read only) to your data file. You can refer to tech tip ref #s 32842, 27584, and 28672 on how to detect a locked structure or data file.